A seamless texture traced from an image on opengameart.org shared by Scouser.
Source Firkin
A free background pattern with abstract green tiles.
Source V. Hartikainen
Everyone loves a diamond, right? Make your site sparkle.
Source AJ Troxell
Remixed from a design seen on Pixabay. The basic tile can be had by selecting the rectangle in Inkscape and using shift+alt+i
Source Firkin
Prismatic Groovy Concentric Background 3
Source GDJ
As far as fabric patterns goes, this is quite crisp.
Source Heliodor Jalba
A seamless pattern the starting point for which was a 'rainbow twist' texture in Paint.net.
Source Firkin
Don’t look at this one too long if you’re high on something.
Source Luuk van Baars
This light background pattern has a texture of "frozen" surface with diagonal stripes. Here's an yet another addition to the collection of free website backgrounds.
Source V. Hartikainen
Prismatic Groovy Concentric Background 5 No Black
Source GDJ
Dark, square, clean and tidy. What more can you ask for?
Source Jaromír Kavan
Derived from an image that was uploaded to Pixabay by starchim01
Source Firkin
From a drawing in 'The Quiver of Love', Walter Crane, 1876
Source Firkin
Prismatic Abstract Background Design
Source GDJ
Seamless pattern the tile for which can be had by using shift-alt-I on the selected rectangle in Inkscape.
Source Firkin
From a design found in 'History of the Virginia Company of London; with letters to and from the first Colony, never before printed', Edward Neill, 1869.
Source Firkin
Remixed from a drawing in 'The Canadian horticulturist', 1892
Source Firkin
A background pattern with wavy green vertical stripes. This one has green stripes on a white background. Download if you like it.
Source V. Hartikainen
Prismatic Geometric Pattern Background
Source GDJ
Zero CC tileable Crackled Cement (streaks) texture, photographed and made by me. CC0
Source Sojan Janso
To get the tile this is formed from select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Seamless Green Tile Background
Source V. Hartikainen
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
It almost looks a bit blurry, but then again, so are fishes.
Source Petr Šulc